Novel Poly(N-vinylcaprolactam-co-2-(diethylamino)ethyl methacrylate) Gels: Characterization and Detailed Investigation on Their Stimuli-Sensitive Behaviors and Network Structure

Abstract

Poly(N-vinylcaprolactam-co-2-(diethylamino)ethyl methacrylate), P(VC-co-DEAEMA), gels were synthesized in ethanol by using free radical cross-linking polymerization method at 60 °C for 24 h in the presence of azobis(isobutyronitrile) (AIBN) as initiator. Homopolymer gels of N-vinylcaprolactam (PVC) and 2-(diethylamino)ethyl methacrylate (PDEAEMA) were also synthesized at the same conditions and used for comparison purposes. In the synthesis of homopolymer and copolymer gels, ethylene glycol dimethacrylate (EGDMA) and allyl methacrylate (AMA) cross-linking agents were employed in order to determine the effects of cross-linker type on the equilibrium swelling value (ESV) and percentage of gelation (PG). pH and temperature sensitivities of gels were investigated for both cross-linkers, and network parameters of gels were also found. In addition, detailed characterization studies were performed by Fourier transform infrared and scanning electron microscopy techniques. It was observed that PVC gel had the lowest PG and highest ESV. Compared to EGDMA, AMA increased thee percentage of gelation and decreased the equilibrium swelling value of gels. pH-sensitive profiles of gels were substantially different from each other and strongly dependent on DEAEMA content. Copolymer gels containing the highest mole percentage of N-vinylcaprolactam (95%) showed non-Fickian and Fickian swelling behavior at pH 7.4 for EGDMA and AMA cross-linkers, respectively. It was found that both monomer concentration and cross-linker type affected the polymer−solvent interaction parameters (χ), mesh size (ζ), and experimental average molecular mass between the cross-links (M c E) of gels.

Poly(N-vinylcaprolactam), a comprehensive review on a thermoresponsive polymer becoming popular

“…The crooslinkers used includes: N,N'-methylene-bis-acrylamide (BIS) [39,141], ethylene glycol dimethacrylate (EGDMA) [128,129,138], triethylene glycol dimethacrylate [105,134], allyl methacrylate (AMA) [128,129], tetraethyleneglycoldiacrylate [138], and 3,3'- [40,41,134,142].…”

“…Various techniques have been used for the synthesis of hydrogels based on PNVCL: free radical cross-linking polymerization [128][129][130] photopolymerization [131,132], radiation polymerization [40,41,[133][134][135], frontal polymerization (FP) [136][137][138], sequential polymerization [139], and sol-gel technology [140].…”

“…The most widely used initiators considering all methods of synthesis of hydrogels are: [104,128,129], aliquat persulfate [136], azobis-4-cyanovaleric acid [125,139], trihexyltetradecylphosphonium persulfate [138,141], photoinitiator Irgacure ® 2959 [131] and photo-initiator Irgacure ® 184 [132]. The crooslinkers used includes: N,N'-methylene-bis-acrylamide (BIS) [39,141], ethylene glycol dimethacrylate (EGDMA) [128,129,138], triethylene glycol dimethacrylate [105,134], allyl methacrylate (AMA) [128,129], tetraethyleneglycoldiacrylate [138], and 3,3'- [40,41,134,142].…”

“…For the hydrogels with DEAEMA comonomer content and crosslinker type affected the experimental average molar mass between the crosslinks M c Exp . Swelling of gels with high content on DEAEMA increased at pH values lower than 7.4 due to protonation of the tertiary amine groups[128]. In the case of IA containing hydrogels, the drosslinker used was AMA and the IA content was only varied up to 10 mol%.…”

“…It was observed that the transition temperature T tr increases with increasing contents of NVP and the ammonium salt in gels. The shift of T tr to higher temperatures is caused by hydrophilicity of network chains increasing with increasing NVP contents[40].akal et al prepared chemically crosslinked NVCL coppolymeric hydrogels with both basic DEAEMA[128] and acidic itaconic acid (IA)[116] comonomers.Conventional free radical crosslinking polymerization at 60 °C using AIBN as an initiator for 24 h was used. In the case of DEAEMA containing hydrogels, the crosslinker was varied EGDMA and allylmethacrylate (AMA) to test their effect in hydrogel properties.…”